The application relates generally to absorption systems. More specifically, the application relates to an automatic purge system used in an absorption system.
Absorption systems may include an absorber, one or more pumps, one or more generators, a condenser, an evaporator, and associated piping and controls. The systems use a fluid that includes absorber or absorbent and refrigerant. The fluid is labeled either strong or dilute, depending on whether the concentration of absorber is relatively high or low. A dilute fluid may contain approximately 56-60 weight percent absorber, for example, lithium bromide. A strong fluid may contain approximately 59-65 weight percent absorber. The exact values depend upon operating temperatures and the design of the absorption system.
During operation of an absorption system, a dilute fluid exits or is pumped from an absorber to a generator, which evaporates refrigerant from the dilute fluid. Since evaporating the refrigerant from the dilute fluid increases the concentration of absorber in the fluid, the fluid is now referred to as a strong fluid. The strong fluid from the generator is returned to the absorber.
The evaporated or vapor refrigerant from the generator condenses to a condensed or liquid refrigerant in a condenser and then flows to an evaporator. In the evaporator, the condensed refrigerant absorbs ambient heat from a process fluid, which provides the desired refrigeration effect, and causes the refrigerant to vaporize.
The vaporized refrigerant from the evaporator flows to the absorber, where the refrigerant is exposed to the strong fluid returning from the generator. The strong fluid absorbs the refrigerant, thereby causing the strong fluid to become a dilute fluid and the process repeats.
Absorption systems may be large systems having complex constructions with many components. In absorption systems there may exist many joints between the components, which may provide the potential for the leakage of air into to the absorption system. Because the operating pressure of absorption systems may be very low, for example less than about six torr, there is an opportunity for the leakage of air into the system to occur. Introduction of air into an absorption system may cause a depletion of corrosion inhibiting chemicals within the absorption system and eventually, may cause internal corrosion, which may lead to a reduction in the performance of the absorption system. In addition, corrosion in the absorption system may produce non-condensable gases that may also cause a reduction in performance of the absorption system. A purge system can be used to remove air and non-condensable gases from the absorption system. A purge system may require an operator or user to frequently monitor the absorption system during operation to determine whether a purge of the air and non-condensable gases is necessary for proper operation of the absorption system.